But it also sounds as though he was willing to forget and forgive to an extent as after the original challenge he left it alone.

Until, that is, a certain Scotch Irish gentleman intruded:
General Mason did not accept (McCarty's challenge), being a Senator of the United States, but after his term had expired, while riding on a stage to Fredericksburg with General Andrew Jackson, the subject of the challenge came up, when Jackson told Mason that his refusal to accept was an injury to his standing and as he was no longer in office he should now challenge McCarty.
Mason being devious, got McCarty to rechallenge him by taking advantage of of the Celt mercurial temperment.

Single Barrel shotguns at four paces. Different...